Modeling of high temperature fuel cells and their integration with turbines

This thesis explores the different parameters that have an impact on the high temperature fuel cells performance and their successful integration in a hybrid system with turbines.; A 1D isothermal electrochemical model that accounts for fuel utilization was derived. The V-I curves using local concentration of species differ from the ones using either the inlet or the outlet concentration. The effect of the water gas shift reaction at the anode was also considered.; We developed a 2D FORTRAN model that combines electrochemistry with heat transfer and simulates temperature and current distribution in a molten carbonate fuel cell (MCFC) and a planar solid oxide fuel cell (SOFC). Both cross-flow and co-flow fuel cell configurations have been considered. The effect of fuel flow rate and fuel utilization in the fuel cell temperature has been investigated.; We considered a fuel cell stack model with 1D layers corresponding to the bottom separator, the fuel channel, the electrolyte/electrode matrix, the air channel and the top separator. This structure has been repeated, in the stacking direction, as many times as the number of cells we would like to include in the stack. A variation in each cell temperature in the stack is observed and temperature distribution and concentration of species have been plotted.; The 2D model has been extended to a 3D model by importing the 2D electrochemistry as heat generation via source terms into the FLUENT software. Temperature contours for the stack has been derived. The 3D temperature field obtained at the solid part using FLUENT is in good agreement with the results of our 2D code when the same operating conditions are imposed. The impact of the thickness of the metallic interconnect has been investigated.; We integrated the fuel cell in a hybrid system with gas and steam turbines in a cogeneration and tri-generation design. A parametric analysis identified the optimal power ratio of fuel cell/gas turbine in a hybrid system that achieves the highest power and cogeneration efficiency. This analysis was done for MCFC and SOFC. We analyzed the effect of fuel cell operating pressure and fuel utilization in the system efficiency.